This program is designed to analyze the host responses which contribute to the immunopathogenesis of murine schistosomiasis mansoni, and determine and evaluate the immunoregulatory mechanisms which develop during the course of this chronic infection. The program will analyze the nature of the soluble suppressive factor produced by cells from chronically-infected mice induced with soluble egg antigenic preparation (SEA). The nature of the passively transferred suppressor cell system, which suppress granuloma formation, will be investigated more fully and analyzed in relationship to possible macrophage suppressor systems. Some work will begin toward the evaluation of immunoregulatory mechanisms in relationship to the partial protection afforded mice to challenge with S. mansoni. The overall program is broadly based and intended to examine the responses and regulations which occur during prolonged exposure to multiple immunogens in this chronic disease setting.